I would like to determine the sign of a algebraic combination of symbols, but Mathematica does not return a value for the Sign function, even if the sign is obvious. For example, if I define:
, then Mathematica returns not the correct result for Sign[a*b], which should be "1", but just returns "Sign[a*b]", indicating that Mathematica is not able to determine the sign of the product of "a" and "b". Is Mathematica in general not able to determine the sign of algebraic combinations of symbols, or is it a mistake of mine?
Thanks for help!